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Related FAQs: Sea
Squirts, Ascidians 2,
Ascidian ID, Ascidian Behavior,
Ascidian Compatibility,
Ascidian
Selection, Ascidian Systems,
Ascidian Feeding, Ascidian Disease,
Ascidian Reproduction,
Related Articles: Live
Rock, Review of Tyree's "Cryptic
Filtration"
Bk, Sponges,
/The Conscientious Reef Aquarist
Almost
Us!? Sea
Squirts, Tunicates, Ascidians, Subphylum Urochordata, Phylum Chordata pt 1.
To: Pt.
2
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By Bob Fenner |
Polycarpa and Atriolum
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Tunicates, Sea Squirts: Grouped within the same phylum in zoological classification as the
vertebrates are a couple of other subphyla of interest to marine aquarists. The
Urochordata don't look much like fishes, birds, mammals, lacking a backbone, but
do share four other important characteristics with them. During larval
development they possess a tail, a dorsal nerve cord, a dorsal (non-bone)
stiffening structure (the notochord), and pharyngeal gill clefts. These "lower" chordates are variously called
tunicates (for their cellulose matter that makes up their body covering), Sea
Squirts (for their apparent and real capacity to forcibly eject water) and
Ascidians (Greek for "little body") for the Class of attached forms.
There are pelagic tunicates, grouped in the Class Thalicea, but these are of
little interest to aquarists.
| A thaliacean "Salp". The (Class) Thaliacea include
about seventy barrel-shaped pelagic animals that filter feed (like all
urochordates), but from one end opening to the other exiting as they
locomote through the water. This Class is further subdivided into three
subclasses. The Pyrosomida are colonial and the Salpida and Doliolida are
not. |
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The Ascidians on the other hand are a major part of the
"cryptic fauna" of live rock... often making up a sizeable
proportion of this material (second only to sponges). Though they may not be
easily recognized, tunicates are among the most common marine invertebrates, and
an important functional component, for aquarists as well.
Some Common, Colorful Species:
| Aplidium crateriferum Savigny 1816, Crater Sea
Squirt. Tropical Indo-Pacific; Red Sea to Western Pacific. Usually grows
under rocks (here a colony is doing well under a Sarcophyton in Australia
and one in N. Sulawesi). Can be grown in captivity (even reproduced). |
 
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| Aplidium tabascum. Colonies reddish to orange,
opaque. Indo-West Pacific; common in northern Australia. N. Sulawesi
pix. |
 
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| Ascidea sydneiensis Stimpson 1855. Yellow-Green Sea
Squirt. Solitary urn-shaped zooids of up to four inches in height.
Large and few oral siphons. Variable in color. Worldwide in tropical seas.
Hawai'i pic. |
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| Atriolum robustum Kott 1983. South Africa to New
Guinea, Philippines. Small urn-shaped zooids of about an inch in height.
Large and few oral siphons. Most are rust-orange or greenish shades. Often
confused with Didemnum molle which has much smaller oral siphons. Color due to the endosymbiotic algae Prochloron. |
 
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| Botrylloides species. Row Encrusting Tunicate.
Tropical western Pacific to the Red Sea. Low growing colonies with
distinctive rows of individuals and round chimneys. Red Sea images. |
 
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| Botrylloides sp. N. Sulawesi (Lembeh Strait)
images. |
 
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| Clavelina sp. Bulb Tunicates. Grow in clusters. These
ones common in Florida, Bahamas, the Caribbean. Here attached to a clam
which is in turn attached to a gorgonian. |
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| Clavelina cyclus Herdman 1886, the Pale Club Sea
Squirt. Tropical Indo-West Pacific. Less than an inch in height. Not
easily kept... short lived (about a year), not known to reproduce in
captivity. |
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| Clavelina diminuta Kott 1957. Western Pacific;
Australia, Indonesia, Philippines. Colonies form masses of rounded heads
of highly variable color. Kott (1990) moved this species to the genus Pycnoclavella.
Off the north (Gilis) of Lombok, and N. Sulawesi, Indo. |
 
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| Clavelina moluccensis (Sluiter 1904). Australia,
Indonesia, Singapore, Philippines. Colonies occur as many ovoid zooids on
thick stalks. Color varies from dark to light blue to violet. One
colony off Pulau Redang, Malaysia, another off Queensland, Austr.. |
 
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| Clavelina picta, the Painted Tunicate. Florida,
Bahamas, Caribbean. Frequently found in clusters of hundreds of
individuals hanging on to gorgonians, black coral, sponges. Translucent
bodies of variable cool colors. Siphon rims reddish to dark purple. A colony in the Bahamas on a Sea
Fan, and one off St. Thomas. |
 
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| Clavelina robusta Kott 1990. Western Pacific;
Australia, Indonesia. Philippines, Japan, Solomons. Dense clusters of
cylindrical zooids. Dark blue to gray in color with yellow, green or white
rings about both siphons. Here in Bunaken/Sulawesi/Indo. |
 
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| Clavelina sp. and a "marauding" flatworm, Pseudobiceros
species that resembles the nudibranch, Glossodoris atromarginata
(Cuvier 1804) feeding upon the colony. N. Sulawesi images. |
 
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To: Pt. 2
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